怎么做一个跟随鼠标的可设定的时间倒计时显示。帮帮我~~~~~~~~~~~~~~~~

<HTML>
<HEAD>
<META NAME="GENERATOR" Content="Microsoft Visual Studio 6.0">
<TITLE></TITLE>
</HEAD>
<BODY><DIV ID=detail style="Z-INDEX: 3;  WIDTH: 200px; POSITION: absolute; HEIGHT: 50px"></DIV></BODY>
</HTML>
<script language="javascript">
var now = new Date();
now.setTime(1000*3); // 倒计时的时间window.setTimeout("setTime()",1000);function setTime() {
now.setTime(now.getTime() -1000);
detail.innerHTML = "还有：" + now.getUTCHours() + ":" + now.getUTCMinutes() + ":" + now.getUTCSeconds() + "，网页将自动关闭！";
if(now.getTime() == 0)
window.close();
window.setTimeout("setTime()",1000);}function mousemove() {detail.innerHTML = "还有：" + now.getUTCHours() + ":" + now.getUTCMinutes() + ":" + now.getUTCSeconds() + "，网页将自动关闭！"; detail.style.left = event.x;
detail.style.top = event.y;
}
window.document.onmousemove=mousemove;
</script>